BOSTON -- Siblings of middle-age stroke patients have nearly twice the risk of strokes themselves compared with the average American.

Action Points

Explain to patients that previous studies have shown Mexican Americans to be at higher risk for stroke than non-Hispanic whites, and this population-based suggests that genetic, environmental, or cultural factors may play a part.

This study was published as an abstract and presented as a poster and orally in a briefing at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.

BOSTON, May 4 -- Siblings of middle-age stroke patients have nearly twice the risk of strokes themselves compared with the average American.

Among 807 brothers and sisters of 181 men and women who had strokes or TIAs before the age of 65, the relative risk for stroke was 1.92, compared with national stroke prevalence estimates, said Lynda D. Lisabeth, Ph.D., of the University of Michigan, and colleagues, at the American Academy of Neurology meeting here.

The risk for stroke among the siblings of stroke victims was particularly high among Mexican Americans in general, and Mexican-American men in particular in a community-based study, reported co-author Lewis B. Morgenstern, M.D., also of the University of Michigan in Ann Arbor.

"If we compare Mexican Americans to non-Hispanic whites, we find that the risk to the sibling is especially prominent in Mexican Americans, with over a doubling of the risk compared to the general population," said Dr. Morgenstern. "The risk is not as substantial in non-Hispanic whites as it is Mexican Americans."

Among non-Hispanic whites, only the siblings of women who had strokes were at increased risk for a stroke.

The authors looked at family groupings of patients who had ischemic strokes or TIA from the ages of 45 to 64. A random subset of patients were interviewed to determine the number of biologic siblings and the history of stroke among them.

The investigators calculated relative risk ratios for the overall population and by ethnic background, using national prevalence estimates for the general population.

They found that overall, siblings of stroke victims had a relative risk for stroke of 1.92 (95% confidence interval, 1.39-2.61). Among Mexican Americans as a whole, the risk was exactly double (relative risk 2.00, 95% CI, 1.39-2.81).

This result was because of a significantly higher risk among siblings of Mexican-American men who had stroke (relative risk 2.61; 95% CI, 1.64-3.99); the relative risk for siblings of Mexican Women was not significant (1.47, 5% CI: 0.83-2.46).

Among non-Hispanic whites, only the brothers and sisters of women who had stroke were themselves at increased risk for stroke (relative risk 2.76, 95% CI, 1.22-5.66).

Because this was a population-based study, the authors were not able to control for potential confounders such as genetics, environment, cultural differences, or familial factors, Dr. Morgenstern said.

"We've already shown in other research that Mexican-Americans have a higher risk of stroke compared to non-Hispanic whites, and on top of that we're now able to show that their siblings have more risk of stroke, they have more siblings [than whites], and are more likely to be in the same geographic area [as siblings], which makes them a great population to study as we further genetics research," he concluded.

The study was funded by the National Institutes of Health. The authors had no financial disclosures relevant to the study.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco

MedPageToday is a trusted and reliable source for clinical and policy coverage that directly affects the lives and practices of health care professionals.

Physicians and other healthcare professionals may also receive Continuing Medical Education (CME) and Continuing Education (CE) credits at no cost for participating in MedPage Today-hosted educational activities.